Development of a mechanistic resin release model for low-level waste source term analysis.

摘要

o describe the release of radionuclides from ion-exchange resins, which represents one of the most important waste streams in LLW management, a new resin release model was developed based on the descriptions of the resin bead phase and the bulk pore water phase within waste containers. This modeling setup provides the capability to describe all the physical processes taking place for the release of radionuclides. Due to the difficulty in obtaining analytical solutions, a numerical solution approach was employed in this model. The numerical approach of the model was validated through comparisons of test case solutions with analytical solution approaches. For the LLW disposal facility source term analysis, a modular mechanistic systems model was developed. The model is capable of describing key processes of importance that lead to the disposal facility source term, including the description of time-dependent water infiltration changes with the failure of engineered barriers, the stochastic nature of waste container failure processes, and release of radionuclides from various LLW forms.;By using the new resin release model, key processes and parameters in describing radionuclide release were identified. These are ionic strength of the leachant water, flow rate of infiltration water, diffusion within the bulk pore water phase, and sorption during the transport in the bulk pore water phase. Some of the parameters are found to have little impact in describing the phenomena. These include the interdiffusion coefficient within resin beads, and density and radius of resin beads. Other existing simplified modeling approaches are compared with the new resin release model and validities of using these simplified models are discussed.;The new LLW disposal facility source term model developed in this research is composed of the water infiltration model, the waste package failure model, the radionuclide release model, and the near-field transport model. The resin release model developed in this research was incorporated into this model. The model was used to identify the major sources of uncertainty in the predictions of LLW source term based on a reference test case analysis with